1. Field of the Invention
The present invention relates to an imprint apparatus and a method of manufacturing an article used in the imprint apparatus.
2. Description of the Related Art
An imprint technique is already known as a technique that replaces a method of forming a micro-pattern on a semiconductor device using photolithography by ultraviolet rays, X-rays, or an electron beam. The imprint technique transfers a pattern on a resin by pressing a mold formed with a micro-pattern against a substrate such as a wafer coated with a resin material. The imprint technique includes some types. As one method, a photo-curing method is proposed by PCT Publication(WO) No. 2005-533393. The photo-curing method exposes an ultraviolet-curing resin against which a transparent mold is pressed, and then removes (releases) the mold after curing. The imprint technique based on this photo-curing method is suited to the manufacture of semiconductor integrated circuits since it allows relatively easy temperature control and observation of alignment marks on a substrate via the transparent mold. In consideration of different patterns to be superposed, a step-and-repeat method, which prepares a mold to fit the size of a chip of a device to be manufactured, and sequentially transfers the patterns onto respective shots on a substrate can be applied.
In an imprint apparatus based on the photo-curing method, an uneven thickness of an ultraviolet-curing resin (to be referred to as a resin hereinafter), which is called a residual layer and is present between the substrate surface and concave bottom surface of a concave-convex pattern after pattern transfer poses a problem. This is because when the thickness of the residual layer (residual layer thickness) of the resin is uneven, the width of a convex portion of the concave-convex pattern locally changes in an etching process executed for the substrate after pattern transfer, and the line width precision of a transfer pattern is adversely affected. In the imprint apparatus, the presence of dust also poses a serious problem, and the concave-convex pattern of the mold may often be destroyed at the time of pattern transfer depending on the size and material of dust. In any case, when transfer is continuously made on shots on the substrate intact, it is not preferable since the number of defective shots merely increases. When transfer errors such as the residual layer thickness unevenness of the resin and the presence of dust are confirmed, pattern transfer has to be aborted. PCT Publication(WO) No. 2007-523492 discloses a method of checking changes between shots by comparing characteristics of a plurality of shots on a single substrate as a transfer quality determination method.
However, with the method described in PCT Publication(WO) No. 2007-523492, when shot characteristics are different for respective substrates, criteria for determining transfer qualities for respective substrates also become different, thus posing another problem. Also, with the method described in PCT Publication(WO) No. 2007-523492, since a transfer quality is determined based on changes between shots, the quality of the first shot cannot be determined.